Devices for introduction into a body via a substantially  straight conduit to form a predefined curved  configuration, and methods employing such devices

ABSTRACT

A device for introduction into a body in a straight configuration and assuming within the body a predefined curved configuration, includes an elongated element formed from a number of segments interconnected so as to form effective hinges therebetween. When the elongated element is confined to a straight state, the effective hinges transfer compressive forces from each segment to the next so that the elongated element can be pushed to advance it through a conduit. When the elongated element is not confined to a straight state, the effective hinges allow deflection of each segment relative to adjacent segments until abutment surfaces of the segments come into abutment, thereby defining a fully flexed state of the elongated element with a predefined curved configuration. The device can be produced with a wide range of two-dimensional and three-dimensional curved forms, and has both medical and non-medical applications.

This is a continuation of application Ser. No. 12/960,503 filed Dec. 5,2010, which is a continuation of application Ser. No. 11/813,213 filedJul. 2, 2007, now issued as U.S. Pat. No. 7,918,874, which is acontinuation of Application No. PCT/IL05/001393 filed Dec. 28, 2005,which is a continuation-in-part of application Ser. No. 11/028,655 filedJan. 5, 2005, now issued as U.S. Pat. No. 7,503,920.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to devices for introduction into a bodyvia a substantially straight conduit to form a predefined curvedconfiguration, and methods employing such devices.

It is known to insert straight elements into various types of bodies. Inthe general field of mechanical engineering, this includes insertion ofdrills, nails, screws and rods of various kinds into structures such aswalls, articles such as furnishings, other inanimate bodies, plantbodies such as wood, and animal or human bodies. In certain cases, thestraight elements have structures or mechanisms for securing theelements against withdrawal from the body.

It is also known in certain contexts to insert elements with a fixeddegree of curvature into a body. Examples of this kind include curvedneedles such as are used for sewing leather, and arcuate drills formedical applications, such as described in U.S. Pat. No. 4,312,337 toDonohue and U.S. Pat. No. 4,941,466 to Romano. Such structures arelimited to a very superficial depth of penetration into the body, andgenerally channel through an arc of less than 180° within the body.

In a third group of applications, primarily limited to the field ofmedical endoscopy, steerable flexible elements are introduced into abody. Steerable flexible elements can be introduced through straightconduits and can then be deflected within the body in order to steerthem to a desired location, thereby allowing the elements to reach alocation at an arbitrary desired depth within a body. These elements,however, do not generally assume a well defined curved configurationwithin the body, and typically do not turn through angles of more thanabout 180°. In many cases, steerable elements are specifically kept awayfrom their mechanical limit of flexing in order to avoid structuraldamage through over-flexing.

None of the above provide a structure or method through which a curvedstructure can be introduced into a body via a straight conduit and thenassumes a deployed position in a predefined curved configuration withinthe body, and particularly where the predefined curved structure turnsthrough more than 180°, has a variable curvature and/or assumes a threedimensional (non-planar) geometry.

There is therefore a need for devices for introduction into a body via asubstantially straight conduit to form a predefined curvedconfiguration, and methods employing such devices.

SUMMARY OF THE INVENTION

The present invention is a device for introduction along a guide into abody and assuming within the body a predefined curved configuration.

According to an embodiment of the present invention there is provided, amethod for stabilizing the spinal column of the body of a mammaliansubject, the method comprising the steps of: (a) providing an elongatedelement configured such that: (i) the elongated element assumes asubstantially straight state for introduction into the body; and (ii)the elongated element assumes a curved configuration within the body;(b) introducing the elongated element into the body in the substantiallystraight state; (e) causing the elongated element to assume the curvedconfiguration within the spinal column, thereby defining an at least apartial enclosure; and (d) introducing a quantity of biocompatiblestructural filler material into the at least partial enclosure so as tostabilize the spinal column.

According to a further feature of an embodiment of the presentinvention, the curved configuration is deployed within a vertebral bodysuch that the curved configuration and the filler material achievekyphoplasty.

According to a further feature of an embodiment of the presentinvention, the curved configuration is deployed between two vertebralbodies such that the curved configuration and the filler materialachieve fusion of the two vertebral bodies.

According to a further feature of an embodiment of the presentinvention, the biocompatible structural filler material comprises atleast one material selected from the group of materials consisting of:bone cement; flexible biocompatible fillers; and osteo-inductivematerials for promoting bone growth; bone grafts; and bone marrow.

According to a further feature of an embodiment of the presentinvention, the elongated element is formed with a plurality of effectivehinges spaced along its length.

According to a further feature of an embodiment of the presentinvention, the effective hinges are at an oblique angle to a directionof elongation of the elongated element such that the curvedconfiguration of the elongated element exhibits three-dimensionalcurvature.

According to a further feature of an embodiment of the presentinvention, the curved configuration includes a plurality of non-coplanarloops.

According to a further feature of an embodiment of the presentinvention, the curved configuration includes a conical spiral.

According to a further feature of an embodiment of the presentinvention, the curved configuration includes a helix.

According to a further feature of an embodiment of the presentinvention, the curved configuration includes at least one loop closed onitself so as to generate a region of overlap, and wherein lateralsurfaces of the elongated element are formed with complementaryinterlocking features so as to inhibit lateral displacement of oneregion of the at least one loop relative to an overlapping portion ofthe at least one loop.

According to a further feature of an embodiment of the presentinvention, the at least one loop is implemented as a plurality of loopsin at least partially overlapping relation.

There is also provided according to an embodiment of the presentinvention, a method for stabilizing the spinal column of the body of amammalian subject, the method comprising the steps of: (a) providing anelongated element having a plurality of effective hinges, the elongatedelement being configured such that: (i) the elongated element assumes asubstantially straight state for introduction into the body; and (ii)the elongated element is deflected at the effective hinges to assume acurved configuration within the body; (b) introducing the elongatedelement into the spinal column in the substantially straight state; (c)causing the elongated element to assume the curved configuration withinthe spinal column, thereby defining an at least partial enclosure; and(d) introducing a quantity of biocompatible structural filler materialinto the at least partial enclosure so as to stabilize the spinalcolumn.

According to a further feature of an embodiment of the presentinvention, the curved configuration is deployed within a vertebral bodysuch that the curved configuration and the filler material achievekyphoplasty.

According to a further feature of an embodiment of the presentinvention, the curved configuration is deployed between two vertebralbodies such that the curved configuration and the filler materialachieve fusion of the two vertebral bodies.

According to a further feature of an embodiment of the presentinvention, the biocompatible structural filler material comprises atleast one material selected from the group of materials consisting ofbone cement; flexible biocompatible fillers; and osteo-inductivematerials for promoting bone growth; bone grafts; and bone marrow.

According to a further feature of an embodiment of the presentinvention, the effective hinges are at an oblique angle to a directionof elongation of the elongated element such that the curvedconfiguration of the elongated element exhibits three-dimensionalcurvature

According to a further feature of an embodiment of the presentinvention, the curved configuration includes a plurality of non-coplanarloops.

According to a further feature of an embodiment of the presentinvention, the curved configuration includes a helix.

According to a further feature of an embodiment of the presentinvention, the curved configuration includes at least one loop closed onitself so as to generate a region of overlap, and wherein lateralsurfaces of the elongated element are formed with complementaryinterlocking features so as to inhibit lateral displacement of oneregion of the at least one loop relative to an overlapping portion ofthe at least one loop.

According to a further feature of an embodiment of the presentinvention, the at least one loop is implemented as a plurality of loopsin at least partially overlapping relation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 is an isometric view of a first implementation of a device,constructed and operative according to the teachings of the presentinvention, for introduction into a body via a substantially straightconduit to form a predefined curved configuration;

FIG. 2 is a side view of the device of FIG. 1 during insertion along astraight conduit, the conduit being cut-away for clarity ofpresentation;

FIG. 3 is a view similar to FIG. 2 showing the device extending beyondthe straight conduit and assuming a predefined curved configuration;

FIG. 4 is an isometric view of a second implementation of a device,constructed and operative according to the teachings of the presentinvention, for introduction into a body via a substantially straightconduit to form a predefined curved configuration, the device having ahollow central channel;

FIG. 5 is a side view of the device of FIG. 4 during insertion along astraight conduit, the conduit being cut-away for clarity ofpresentation;

FIG. 6 is a view similar to FIG. 5 showing the device extending beyondthe straight conduit and assuming a predefined curved configuration;

FIG. 7 is an isometric view of a third implementation of a device,constructed and operative according to the teachings of the presentinvention, for introduction into a body via a substantially straightconduit to form a predefined curved configuration, the device having acircular cross-sectional shape;

FIG. 8 is an isometric view of a fourth implementation of a device,constructed and operative according to the teachings of the presentinvention, for introduction into a body via a substantially straightconduit to form a predefined curved configuration, the device having asemicircular cross-sectional shape;

FIG. 9A is a front view of a fifth implementation of a device,constructed and operative according to the teachings of the presentinvention, for introduction into a body via a substantially straightconduit to form a predefined curved configuration, the device havingoblique effective hinges between adjacent segments;

FIG. 9B is an isometric view of the device of FIG. 9A;

FIG. 10 is a view similar to FIG. 9A showing the device in itspredefined curved configuration;

FIG. 11 is a side view of a sixth implementation of a device,constructed and operative according to the teachings of the presentinvention, for introduction into a body via a substantially straightconduit to form a predefined curved configuration, the device having afirst region configured to produce a predefined curved configurationwith a first radius of curvature and a second region configured toproduce a predefined curved configuration with a second radius ofcurvature;

FIGS. 12A, 12B and 12C are side views of the device of FIG. 11 at threestages during insertion along a straight conduit, the conduit beingcut-away for clarity of presentation;

FIG. 13 is an isometric view of a seventh implementation of a device,constructed and operative according to the teachings of the presentinvention, for introduction into a body via a substantially straightconduit to form a predefined curved configuration, the device having apredefined shape corresponding to a conical helix;

FIG. 14 is a front view of an eighth implementation of a device,constructed and operative according to the teachings of the presentinvention, for introduction into a body via a substantially straightconduit to form a predefined curved configuration, the device having apredefined curved shape including both a flat spiral with a closedcylindrical helix;

FIGS. 15A and 15B are a partial schematic isometric view, and a partialschematic side view, of part of a device according to the presentinvention showing an arrangement for interlocking between adjacentsegments of the device, the device being shown in its straight andcurved states, respectively;

FIGS. 16A and 16B are a partial schematic isometric views of part of adevice according to the present invention showing an alternativearrangement for interlocking between adjacent segments of the device,for a solid and hollow device, respectively;

FIGS. 17A and 17B are isometric cut-away views of a device according tothe present invention showing an arrangement for interlocking betweenadjacent coils of a predefined curved shape corresponding to a closedhelix;

FIGS. 18A and 18B are schematic partial side views of a device accordingto the present invention in its predefined curved shape and itsstraightened shape, respectively, showing an implementation of hingedinterconnection for an arbitrarily curved shape;

FIGS. 19A-19C are schematic isometric, longitudinal cross-sectional andend views, respectively, of an individual segment for use in a furtherimplementation of a device according to the teachings of the presentinvention;

FIGS. 19D and 19B are schematic longitudinal cross-sectional views of adevice formed from a plurality of the segments of FIGS. 19A-19C, thedevice being shown in its straightened state and predefined curvedshape, respectively;

FIG. 20A is a schematic side view of components of a drill assembly,constructed and operative according to the teachings of the presentinvention;

FIG. 20B is a schematic side view of the drill assembly of FIG. 20Aassembled;

FIG. 20C is a schematic cross-sectional view through the drill assemblyof FIG. 20B;

FIGS. 21A and 21B are schematic side views, taken at orthogonal angles,illustrating the operation of the drill assembly of FIG. 20A;

FIGS. 22A-22C are schematic illustrations of an implementation of thepresent invention for posterior cervical bone anchoring usingquadru-cortical bone engagement;

FIGS. 23A-23C are schematic illustrations of an implementation of thepresent invention for anterior cervical bone anchoring usingquadru-cortical bone engagement;

FIG. 24 is a schematic illustration of an implementation of the presentinvention for inter-vertebral disc reinforcement;

FIGS. 25A-25C are schematic lateral, anterior and axial views,respectively, showing an implementation of the present invention forinter-vertebral disc replacement;

FIG. 26A is a schematic lateral view showing an implementation of thepresent invention for inter-vertebral disc replacement with adjustableheight restoration;

FIGS. 26B and 26C are axial cross-sectional views taken along lines B-Band C-C, respectively, in FIG. 26A;

FIGS. 27A-27C are schematic posterior views of two adjacent vertebraeduring progressive correction of scoliosis as a minimally invasiveprocedure according to the present invention;

FIGS. 28A-28C are schematic sagittal cross-sectional views illustratingthree variant implementations of multiple-segment vertebral bodyreinforcement according to the present invention;

FIG. 29A is a sagittal cross-sectional view illustrating a spinal columnwith healthy vertebrae;

FIG. 29B is a view similar to FIG. 29A illustrating a collapsedvertebra; and

FIG. 29C is a view of the spinal column of FIG. 29B illustratingschematically the restoration of vertebral height according to theteachings of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a device for introduction into a body via asubstantially straight conduit to form a predefined curvedconfiguration, and methods employing such a device.

The principles and operation of devices and methods according to thepresent invention may be better understood with reference to thedrawings and the accompanying description.

By way of introduction, the present invention provides a family ofdevices all based on a common inventive concept but varying in theirspecific implementations, and most notably, in the specific predefinedcurved form which the devices are configured to assume when they areinserted into a body. The devices are defined geometrically by theirstructure, and mechanically by their properties, but are not limited touse in any specific field of technology or any specific application.These devices will be described below with reference to FIGS. 1-19E.Then, with reference to FIGS. 20A-29C, a small number of exemplaryapplications employing these devices will be presented, primarily in thefield of medical treatment of the human body.

Referring now to the drawings, FIGS. 1-3 show a first basic illustrationof a device, constructed and operative according to the teachings of thepresent invention, for introduction into a body via a substantiallystraight conduit 20, and assuming within the body a predefined curvedconfiguration.

In general terms, the device of each embodiment of the present inventionincludes an elongated element 10 formed primarily from a plurality ofsegments 12 sequentially interconnected so as to form an effective hinge14 between adjacent segments 12. Segments 12 and effective hinges 14 areconfigured such that: (a) when the elongated element 10 is confined to asubstantially straight state, effective hinges 14 transfer compressiveforces from each segment 12 to the next so that the elongated element 10can be pushed so as to advance through substantially straight conduit20; and (b) when elongated element 10 is not confined to a substantiallystraight state, effective hinges 14 allow deflection of each segment 12relative to adjacent segments 12 until at least one abutment surface 16of each segments comes into abutment with at least one correspondingabutment surface 18 of each adjacent segment, thereby defining a fullyflexed state of elongated element 10 corresponding to a predefinedcurved configuration of the elongated element.

It will immediately be clear that the device of the present inventionthus defined is capable of insertion into a body to any desired depth,since it initially follows a substantially straight path, and thendeploys within the body to form a predefined curved structure in whichadjacent segments are interconnected at an effective hinge and abut viaat least one additional surface, thereby providing considerablemechanical stability. Thus, a wide range of curved or convolutedstructures can be introduced temporarily or permanently via an insertionopening which has dimensions corresponding to the cross-sectionaldimensions of the elongated element making up the final shape.

The devices of the present invention may thus be used for a wide rangeof applications including, but not limited to: forming a curved channelthrough a body; cutting-out a sample of material from a body; providinga curved anchoring structure within a body; joining together two partsof a body; aligning two parts of a body; forming a reinforcing structurewithin a body; filling a region of a body; and expanding a spacingbetween parts of a body.

The transition from the substantially straight configuration of thedevice to the predefined curved configuration can be achieved in anumber of ways. According to a first set of implementations, elongatedelement 10 is resiliently biased so as to tend to deflect towards itspredefined curved state. This may be achieved through pre-biasing ofeffective hinges 14 or by addition of supplementary springs or otherresilient elements (not shown). In an alternative set ofimplementations, the geometry of elongated element 10 is chosen suchthat mechanical resistance during insertion of element 10 into a bodycauses deflection of the device to its curved state. According to eitherof the above options, flexing of the device is progressive, occurringcontinuously as the device is extended beyond the delivery conduit 20.According to a further alternative, a selectively operable mechanism(not shown), such as one or more drawstring, may be provided forallowing a user to selectively induce deflection to the predefinedcurved configuration.

As already mentioned, the present invention can be used in a wide rangeof fields of application including, but not limited to, building,mining, industrial applications, carpentry, and medicine. Accordingly,the “body” within which the device is deployed may be any body,including but not limited to: a human body; an animal body; wood; otherbiological materials; walls; furniture; minerals; and other inanimateobjects. Clearly, the dimensions, materials and other design parametersfor the device of the present invention must be selected to render itsuited to the intended application, as will be clear to one ordinarilyskilled in the field of applications for which it is to be used.

Turning now to structural features of specific implementations of thedevice of the present invention, elongated element 10 as illustrated inFIG. 1 is preferably formed from a single elongated rod of rectangularcross-section from which a series of transverse slots are cut tosubdivide the elongated element into segments 12. The relatively thinconnecting bridge of material left beneath the slots renders theinterconnections flexible, thereby providing effective hinges 14. Theslots are shown here as V-shape slots, corresponding to sloped endsurfaces of segments 12. Other slot shapes, such as U-shaped slots,rectangular slots, and more complex shaped slots, may also be used.

It will be appreciated that the structure shown provides all thestructural features of the device of the present invention in a verystraightforward and easily manufactured manner, simply by formingappropriately shaped and positioned slots in a rectangular rod.Effective hinges 14 are thus integrally formed as flat connectingportions of flexible material interconnecting between adjacent segments.The term “flat” is used in this context to refer to the cross-sectionalshape, namely, that in cross-section along the effective axis of thehinge, the thickness of the integral hinge is significantly less thanits width, thereby providing a well-defined direction of flexing. Theintegral hinge may have significant length extending between segments 12(as illustrated in certain examples below) or may have minimal length(such as illustrated here). Effective hinges 14 preferably provideresistance to relative motion of adjacent segments 12 other than theintended hinged motion, thereby avoiding unwanted torsional deformationof elongated element 10.

Clearly, if the device is constructed by cutting slots in an initiallystraight rod of material, and unless the elongated element is furthertreated to change its properties, the unstressed state of the elongatedelement will be in the straightened configuration. According to aparticularly preferred option illustrated here, elongated element 10terminates in a beveled distal tip 22 angled so as to tend to deflectthe elongated element into the fully flexed state as the elongatedelement advances through a medium. Specifically, the beveled distal tip22 preferably has a leading edge on the side from which the slots arecut and a bevel surface facing away from the side of slots. This shape,when advanced into a compressible or displaceable medium, tends to bedeflected so as to follow a curved path, thereby bending elongatedelement 10 progressively towards its fully flexed curved form as itadvances beyond delivery conduit 20, as shown in FIG. 3.

The dimensions of the device of the present invention are chosenaccording to the intended application and the required predefined curvedshape which is to be formed. Thus, at one extreme, for use in hollowingout a subterranean tunnel or an underwater tunnel, an element with awidth and height of one meter or more may be used. At the other extreme,certain delicate medical applications may use an elongated element witha width and height of 5 millimeters or less. For a wide range ofdomestic and medical applications, lateral dimensions of 1-30 mm aresuitable.

In terms of relative dimensions, elongated element 10 is termed“elongated” in the sense that its length is significantly longer thanboth its width and its height. Most preferably, a length of elongatedelement 10 is at least ten times greater than each transverse dimension(height and width) of the elongated element. Preferably, the device isconfigured to form a predefined curved configuration including an arcturning through an angle of at least 180′, and in many cases, passingthrough one or more complete revolutions as will be illustrated in anumber of examples below.

The materials for the device of the present invention are also chosenaccording to the intended application and the mechanical and otherproperties which are required, and may be any suitable materials. Formany applications, various metals and metal alloys (referred tocollectively as metallic materials) are suitable. For some applications,various plastics and other polymer materials are suitable. Otherpossibilities include, but are not limited to, composite materials andceramic materials. For medical applications, biocompatible are used,typically either metallic materials or polymers such as PEEK.

It will be noted that the terms “two-dimensional” and “planar” are usedto refer to the geometry of the predefined curved configuration ofcertain embodiments such as those of FIGS. 1-8 and 11-12C, whereas theterms “three-dimensional” and “non-planar” are used to refer to thegeometry of the predefined curved configuration of embodiments such asthose of FIGS. 9A-10, 13 and 14. These terms are used to classify thenature of the curvature exhibited, i.e., that a circle or flat spiral isa “planar” geometry whereas a helix or cone is a “non-planar” geometry.Clearly, even the “planar” geometry implementations also occupy space inthree dimensions due to the width of the elements.

In the example of FIGS. 1-3, elongated element 10 is cut from a solidrod such that each segment 12 is formed as a non-hollow block ofmaterial. Although the unitary construction with the effective hinges 14integrally formed with the segments 12 is believed to be advantageous,it should be noted that alternative implementations of effective hinges14 also fall within the scope of the present invention. By way ofexample, a first alternative implementation employs a flexible strip asa backbone for the device to which segments 12 (separate blocks) areattached by any suitable attachment technique. An example of this kindis illustrated below with reference to FIGS. 19 a-19E. A secondalternative implementation employs a pivotal interlocking hingearrangement, of a type either with or without a hinge pin, forconnecting between initially separate segments 12.

Substantially straight conduit 20 may be any suitable conduit,preferably close-fitting to the external shape of elongated element 10in its substantially straight configuration. Conduit 20 may be made ofsimilar materials to elongated element 10, or may be made from any othermaterials which are compatible with the intended application.Furthermore, although conduit 20 is the preferred example of a structurefor restricting elongated element to a substantially straightconfiguration during a first part of insertion into a body, it should benoted that other alternatives also fall within the general scope of thepresent invention. Thus, for example, in hollow implementations (such aswill be described below with reference to FIGS. 4-6), an equivalenteffect may be achieved using a centrally deployed rail passing at leastpartially within elongated element 10 which restricts a part ofelongated element 10 to its straight configuration.

Turning now to FIGS. 4-6, these show a second implementation of thedevice of the present invention. This implementation is generallysimilar to that of FIGS. 1-3, differing in two respects, as will now bedetailed.

Firstly, in this implementation, the slots are formed as rectangularslots, so that the abutment surfaces 16 and 18 are only along the upperedges of the adjacent segments. This form has certain advantages ofsimplicity of manufacture, and is also less sensitive to the presence offoreign matter between the abutment surfaces interfering with the curvedconfiguration. On the other hand, the curved structure has triangularlateral openings between adjacent segments which may be undesirable forcertain applications.

Secondly, this implementation is formed from a hollow rod, resulting inan elongated element 10 in which each segment 12 is a hollow block ofmaterial. The resulting central channel through elongated element 10 maybe useful for a wide range of functions, including but not limited to:cutting out a sample of material from a body; excavating a volume ofmaterial from a body; insertion of a flexible tool through elongatedelement 10 to reach a target location within a body; delivering aquantity of fluid or other material to a target location within a body;providing a drive shaft for a drilling tool or other tool located at thedistal end of elongated element 10; relaying illumination and/or imagesto/from a target location within a body; filling with cement to fix adeployed configuration of elongated element 10; and filling elongatedelement 10 with other materials for imparting desired properties toelongated element 10 or surrounding regions of a body.

In all other respects, the structure and function of the implementationof FIGS. 4-6 can be fully understood by analogy with the structure andfunction of the implementation of FIGS. 1-3 described above.

Turning now to FIGS. 7 and 8, it should be noted that elongated element10 may be implemented with a wide range of different cross-sectionalshapes. Thus, by way of examples, FIG. 7 shows an implementation inwhich elongated element 10 is substantially circular in cross-section.In this case, effective hinges 14 are preferably formed as integralhinges by leaving a portion corresponding to a chord of the circlebridging between adjacent segments 12. FIG. 8 shows an implementation inwhich elongated element 10 is substantially semi-circular. Effectivehinges 14 interconnecting segments 12 are preferably formed at the flatside of the elongated element.

Turning now to FIGS. 9A, 9B and 10, these illustrate an implementationof the device of the present invention generally similar to that ofFIGS. 1-3 but wherein the predefined curved configuration is a helix. Toachieve this result, the slots between adjacent segments 12, andtherefore the axes of effective hinges 14, are at an oblique anglerelative to a direction of elongation of elongated element 10. This isseen most clearly in the plan view of FIG. 9A where angle α denotes theinclination of the effective hinge axes relative to a line perpendicularto the direction of extension of elongated element 10. The result ofthis oblique angle of the effective hinges 14 is that the predefinedcurved configuration includes a lateral component of curvature, therebyforming a helix as shown in FIG. 10. Varying angle of inclination αvaries the pitch of the helix, so that the helix can be designed to beeither open as shown (i.e., with space between adjacent coils of thehelix) or closed (i.e., where adjacent coils touch each other).

Turning now to FIGS. 11 and 12A-12C, it should be noted that thepredefined curved configuration of the devices of the present inventiondoes not have to be a uniform configuration with constant curvaturealong the length of elongated element 10. Thus, by way of example, FIG.11 illustrates an elongated element 10 which produces a predefinedcurved configuration (visible in FIG. 12C) including a first region 24having a first radius of curvature R₁ and a second region 26 having asecond radius of curvature R₂ greater than R₁. To achieve this result,the size of segments 12 and their spacing are varied between regions 24and 26 so that a greater degree of deflection occurs between adjacentsegments 12 and/or the segments are more closely spaced in region 24.

FIGS. 12A-12C illustrate the sequence of deployment of the device ofFIG. 11 as it is advanced from conduit 20. As the distal tip ofelongated element 10 first advances beyond conduit 20, it occupies aheight dimension h₁ corresponding substantially to the correspondingdimension of the device in its substantially straight configuration.(The up-down dimension as illustrated is referred to here forconvenience as “height” although the device can clearly be used in anyorientation.) As it advances, region 24 starts to assume its predefinedcurved configuration, thereby defining a part of a substantiallycircular form of diameter (and hence height) h₂ which is twice thesmaller radius of curvature R₁. Then, as elongated element 10 isadvanced further, region 26 progressively extends beyond conduit 20 toform an arc of radius R₂, and hence raising the overall height to h₃(twice R₂). The overall effect is gradual opening of a shape which isreferred to herein as a spiral. Clearly, this effect could be continued,for example by forming a third region of elongated element 10 with moreclosely spaced segments configured to provide a yet larger radius ofcurvature.

It will be noted that the gradual increase in the effective height ofthe device, and in particular, during the transition from h₂ of FIG. 12Bto h₃ of FIG. 12C, renders the device useful as a mechanism for liftinga part of a body, or for separating between two parts of a body. Anexample of such an application will be illustrated below.

It will be noted that the term “spiral” is used herein in its colloquialsense to refer to any shape which spirals inwards/outwards, and is notlimited to a geometric spiral which is referred to herein as a “perfectspiral”. The spiral formed from a stepped increase in radius ofcurvature as described here may be preferred due to its simplicity ofmanufacture. Nevertheless, it will be appreciated that it is possible tovary segment size and/or inter-segment spacing in a continuous manner toachieve a close approximation to a perfect spiral, or any other varyingcurvature profile desired.

Turning now to FIGS. 13 and 14, it should be noted that the principlesof lateral progression described above with reference to FIGS. 9A-10 andof variable curvature described above with reference to FIGS. 11-12C canbe combined to achieve an effectively unlimited range of convolutedthree-dimensional structures in which radius of curvature and axialprogression are arbitrarily chosen according to a specific desiredapplication. FIGS. 13 and 14 illustrate two examples of particularimportance which combine these principles.

Specifically, FIG. 13 illustrates schematically a predefined curvedconfiguration of an elongated element 10 which is formed as a conicalspiral, i.e., a series of coils with sequentially increasing radius ofcurvature combined with axial progression. As before, the variation ofthe radius of curvature may be either continuous (i.e., varying betweeneach adjacent pair of segments) or may be varied in steps, such as everyfew segments, or every 90° or 180° of a coil.

FIG. 14 shows a further preferred example in which a distal part ofelongated element 10 is configured to form a planar spiral 30 (similarto FIG. 12C) and a second portion of elongated element 10 forms a helix32. In this case, helix 32 is preferably a closed helix, i.e., whereeach coil sits in contact with the adjacent coils (referred to as“stacked coils”). This contact between coils renders the shapestructurally strong so that the device can be used for lifting part of abody or separating between two parts of a body, even where considerableforces are involved. At the same time, the presence of the planar spiralat the distal end ensures that a flat surface contacts the body to belifted, thereby avoiding heavy abrasion of the lifted body by theleading end of the elongated element. An application of thisimplementation of the device will be described below.

Turning now to FIGS. 15A-17B, it will be noted that variousmodifications of the shape of segments 12 may be made in order toprovide various forms of interlocking, thereby improving mechanicalstability of the predefined curved configurations of the presentinvention. Thus, FIGS. 15A and 15B show one possible modification inwhich abutment surfaces 16 and corresponding abutment surfaces 18 areconfigured with interlocking features such that, in the fully flexedstate of FIG. 15B, the interlocking features help resist torsionaldeformation of the elongated element. In the example shown here,abutment surfaces 16 are formed with slots 34 while complementaryabutment surfaces 18 are formed with projecting ridges 36 configured forengaging slots 34.

FIGS. 16A and 16B illustrate the same concept implemented without sharpridges and slots, but rather with concavely and convexly curved abutmentsurfaces 16 and 18. FIG. 16B illustrates the same structure as FIG. 16Aimplemented in a hollow embodiment.

Turning now to FIGS. 17A and 17B, these illustrate an additional optionspecifically for closed helical forms such as helix 32 of FIG. 14 inorder to further stabilize the resulting stack of coils. According tothis feature, lateral surfaces of segments 12 are formed withcomplementary interlocking features so as to inhibit lateraldisplacement of successive coils of the helix. In the example of FIG.17A, these complementary interlocking features are implemented as suchas ridges 38 and slots 40. In the example of FIG. 17B, a single step orshoulder 42 is provided. This second option is also useful forstabilizing a closed conical spiral where the difference in radialdimensions between adjacent coils is equal to the width of the singlestep.

Turning now to FIGS. 18A and 18B, these illustrate schematically analternative approach to implementing the device of the present inventionwhich facilitates forming elongated elements with arbitrarily shapedpredefined curved configurations in two or three dimensions, and whichare biased to their curved configurations. Specifically, according tothis approach, an elongated element, typically having a uniformcross-section, is first formed into the desired predefined curvedconfiguration by known techniques. These may include wire or bar shapingtechniques for metallic material, and molding or extrusion for polymermaterials. For three-dimensional shapes, a round cross-section istypically preferred. The elongated element is then cut to form aplurality of slits 44 from the inside of the local curvature of theelement outwards and, in the case of a round cross-section, acorresponding clearance channel 46 from the opposite side of theelement. Most preferably, a round bore 48 is formed at the base of eachslit 44 to spread stresses within the material. This structure thusdefines an elongated element 10 with a plurality of segments 12 formedbetween slits 44 and effective hinges 14 formed between bores 48 andclearance channels 46, allowing the element to be opened up to asubstantially straight configuration as shown in FIG. 18B. Although theexample shown here for simplicity of visual representation is atwo-dimensional form with curvature reversal, it will be appreciatedthat the curvature, and the corresponding hinge axis directions definedby slits 44 and clearance channels 46, can be rotated at arbitrarilychosen angles, allowing substantially any three-dimensional curved shapeto be produced. The resulting structures can be opened up to asubstantially straight configuration as required, but are naturallypre-biased to return to their predefined curved configuration.

Turning now to FIGS. 19A-19E, as mentioned earlier, the devices of thepresent invention may be implemented using a wide variety of structuresfor segments 12 and effective hinges 14. By way of a furthernon-limiting example preferred for certain applications, FIGS. 19A-19Cshow an implementation of a segment 12 formed as a separate block, andFIGS. 19D and 19E show an elongated element 10 formed from a series ofsuch blocks positioned in abutment along a sheet-spring element 60. Thesheet spring 60 passes through channels 62 formed in each segment 12,thereby aligning the segments. The sheet spring is preferably pre-biasedto a curved form so that it returns resiliently to the curved form ofFIG. 19E and can be straightened to the form of FIG. 19D. In the exampleshown here, each segment 10 further features a substantially cylindricalcentral opening 64, openings 64 being aligned in the elongated elementto form a “hollow” element in the sense used above. This round centralchannel is particularly suited to applications such as the flexibledrill shaft described below with reference to FIGS. 20A-21B.

Turning now to applications for the devices of the present invention, itshould be noted that the invention may be used in any situation where itis useful to provide a structure with a predefined curved shape whichcan be straightened into an elongated structure for convenient delivery,such as along a conduit. Examples of types of application for which thepresent invention is useful include, but are not limited to: tunnelingor drilling to form a channel; extracting material; anchoring to a body;clamping together two bodies; providing a reinforcing structure; as afiller structure; as an expander; and as a medical implant.

Depending upon the physical properties of the body into which the deviceis introduced, the device may form its own channel by one or moreprocess including compacting material, displacing material, or, in thecase of hollow embodiments such as in FIGS. 4-6, cutting out a core ofmaterial which enters the hollow of the device. Optionally, a mechanism(not shown) may be provided for mechanically advancing the device intothe material. In other cases, it may be necessary or preferable toprovide the device with active drilling capabilities. One configurationsuitable for implementing the present invention in combination with adrill is illustrated schematically in FIGS. 20A-21B.

Thus, turning to FIGS. 20A-20C, these show a curve-drilling attachment,implemented according to the teachings of the present invention, for usewith a conventional or slightly modified drill. The attachment includesa rotating drill element 50 formed from a rotatable drive shaft of whichat least a portion 52 is flexible and which terminates in a drillingburr 54. The flexible portion 52 of the shaft may be implemented as ahelical spring as shown, or as various other flexible drive elementeffective for transferring rotational power to the drilling burr. Thedrill element 50 is located within a hollow implementation of elongatedelement 10 which is anchored around flexible portion 52 but does notrotate. Around elongated element 10 is an outer conduit 56 which isurged by a spring 58 towards drilling burr 54. As visible in FIG. 20C,the elongated element 10 and outer conduit 56 of the preferredembodiment shown here are implemented with rectangular cross-sections.

FIGS. 21A and 21B illustrate the operation of the drill attachment. Asthe drill is advanced into a body, outer conduit 56 is held back, eitherby being too large to follow the drill element into the hole or due to aflange (not shown) located to define a straight-drilling depth. Onceouter conduit 56 stops advancing, subsequent advancing of the drillelement 50 allows the portion of elongated element 10 beyond the conduitto assume its predefined curved configuration, in this case an arc of acircle, thereby bending the flexible portion 52 so that drilling burr 54follows an arcuate path as seen in FIG. 21B. It should be noted that adrill attachment and corresponding drilling method according to theseprinciples may be used in a wide variety of applications. For example,in household applications, arcuate drilled channels may be used foranchoring to a wall or other object. Similarly, in dental applications,this form of drilling may be important for anchoring implants withinbone. Other non-limiting examples of applications will be discussedbelow.

Parenthetically, it will be noted that this drilling technique can beused for drilling more complex three-dimensional structures. Forexample, if a helical hollow elongated element is used, it is possibleto drill a helical bore through solid material. Such a bore may bevaluable for various applications, including but not limited to, forminga helical cooling channel for pumping a coolant within a cylindricalwall of a cylinder.

Turning now to FIGS. 22A-22C and 23A-23C, these illustrate a furthermedical application of the arcuate drilling technique of the presentinvention for providing bone anchoring. Particularly, the examplesillustrated in these figures relate to anchoring in the cervicalvertebrae, which are considered highly problematic due to the lack ofcancellous bone volume. In contrast to conventional approaches, thispreferred example of the present invention achieves effective anchoringby using four non-collinear regions of engagement which pass throughcortical bone (surfaces). This mode of anchoring is referred to hereinas “quadru-cortical bone engagement”. The four regions of engagement areillustrated by numbered lines in FIGS. 22A and 23A. In the case of FIGS.22A-22C, posterior access cervical bone anchoring is shown, whereas inthe case of FIGS. 23A-23C anterior approach cervical bone anchoring isshown. In both cases, the anchoring element may be the elongated element10 inserted during drilling. Alternatively, the entire drill assemblymay be withdrawn and a separate anchoring element inserted in thechannel.

Turning now to FIG. 24, this illustrates a related technique andcorresponding structure for inter-vertebral disc reinforcement.Specifically, there is shown an elongated element 10 according to thepresent invention passing vertically in a semicircular arc betweenpedicle screws 66 in vertically adjacent vertebrae. The properties ofelongated element 10, and specifically the capability of opening uptoward a lower-curvature state, allow significant relative movementbetween vertebrae for flexion or translation. At the same time, theopposition of the element against bending tighter than its predefinedcurved form provides significant vertical load-bearing ability, therebymaintaining spacing between the vertebrae and relieving pressure fromthe inter-vertebral disc (not shown). Optionally, additional resilientmaterial 68 may be incorporated into elongated element 10 so as toprovide an additional cushioning effect.

Turning now to FIGS. 25A-25C, these illustrate an application of ahelical elongated element of the present invention as an inter-vertebraldisc replacement. In this case, the element 10 is preferably insertedvia a single pedicle screw 66 to which it is fixated after insertion.The external footprint of the helical implant is approximatelycylindrical, and is positioned with its axis directed laterally, therebyproviding support between adjacent vertebrae while allowing flexionmotion.

Turning now to FIGS. 26A-26C, these illustrate a further preferredimplementation of the present invention employing the structure of FIG.14 for inter-vertebral disc replacement with adjustable heightrestoration. In this case, the device is introduced directly between thepedicles into the inter-vertebral volume, preferably previouslyevacuated by a discectomy. As the elongated element it is introduced,the distal part of the elongated element first forms a flat spiral,thereby providing a non-abrasive contact surface for the upper (orlower) vertebra. Then, as the element is advanced further, the closedhelix begins to accumulate, gradually lifting the upper vertebra awayfrom the lower one until the desired height restoration is achieved. Theelongated element is then anchored to a single pedicle screw 66 andsevered to provide an anchored disc replacement.

Turning now to FIGS. 27A-27C, these show schematically a minimallyinvasive procedure according to the present invention for progressivecorrection of scoliosis. In the implementation illustrated here, aspiral implementation of an elongated element is introduced through apedicle delivery screw on the side of the spinal column where vertebralseparation is required. As successive coils of the spiral form, theincreasing diameter of the structure progressively lifts the side of theupper vertebra away from the lower vertebra. This process can beperformed in parallel for a number of vertebrae. If the procedure isperformed using only local anesthetic, the patient can be asked to standbetween adjustments of the vertebral correction, and the adjustments canbe performed iteratively until optimal correction is achieved. Here too,once the required correction has been achieved, the elements are fixatedto the pedicle screw and severed, remaining as implants.

Turning now to FIGS. 28A-28C, these illustrate the use of elongatedhelical implementations of the present invention as multiple-segmentvertebral body reinforcements. Specifically, by employing an elongatedelement 10 with a tight helical form, it is possible to introduce areinforcing element via a single pedicle screw which will then extendvertically through the vertebral bodies and discs of multiple adjacentvertebrae. This provides reinforcement and support for the spinal columnwhile preserving flexibility. The element may extend upwards as shown inFIG. 28A or downwards as shown in FIG. 28B. Since only one pedicle isneeded for introduction of each element, it is further possible tointroduce one element via a first pedicle extending upwards and secondvia the other pedicle extending downwards, as illustrated in FIG. 28C.

Turning now to FIGS. 29A-29C, an implementation of the present inventionfor vertebral height restoration will now be described. Like in theheight restoration for an intervertebral disc described above withreference to FIGS. 26A-26C, this aspect of the present invention is alsoadvantageously implemented using the form of elongated element describedabove with reference to FIG. 14, and in a manner analogous to thatdescribed in FIGS. 26A-26C.

FIGS. 29A and 29B contrast a spinal column with healthy vertebraeagainst another with a collapsed vertebra. FIG. 29C illustrates thespinal column of FIG. 29B after introduction of an elongated element 10according to the teachings of the present invention. The black linesoverlaid over the vertebrae adjacent to the collapsed vertebra of FIGS.29B and 29C show clearly the vertebral height restoration achieved.Optionally, the internal volume within the deployed element may befilled with suitable biocompatible material to impart additionalstructural or therapeutic properties. Examples of structural fillingmaterials include, but are not limited to, bone cement, flexiblebiocompatible fillers and osteo-inductive agents for promoting bonegrowth, including bone grafts and bone marrow. Examples of therapeuticmaterials which can be introduced into the internal volume include, butare not limited to, antibiotics, anti-neoplastic agents and anti-mitoticagents.

Although only a very limited set of examples of applications of thepresent invention have been presented, it will be clear that it may beused in numerous other procedures and treatments in the medical field,as well as in other fields. For example, the various hollowimplementations of the elongated element may optionally be used forsampling tissue, such as for a biopsy, or for removing tissue, such asfor a discectomy.

It will be appreciated that the above descriptions are intended only toserve as examples, and that many other embodiments are possible withinthe scope of the present invention as defined in the appended claims.

1. A method for stabilizing the spinal column of the body of a mammalian subject, the method comprising the steps of: (a) providing an elongated element configured such that: (i) said elongated element assumes a substantially straight state for introduction into the body; and (ii) said elongated element assumes a curved configuration within the body; (b) introducing the elongated element into the body in the substantially straight state; (c) causing the elongated element to assume the curved configuration within the spinal column, thereby defining an at least a partial enclosure; and (d) introducing a quantity of biocompatible structural filler material into the at least partial enclosure so as to stabilize the spinal column.
 2. The method of claim 1, wherein said curved configuration is deployed within a vertebral body such that said curved configuration and said filler material achieve kyphoplasty.
 3. The method of claim 1, wherein said curved configuration is deployed between two vertebral bodies such that said curved configuration and said filler material achieve fusion of the two vertebral bodies.
 4. The method of claim 1, wherein said biocompatible structural filler material comprises at least one material selected from the group of materials consisting of: bone cement; flexible biocompatible fillers; and osteo-inductive materials for promoting bone growth; bone grafts; and bone marrow.
 5. The method of claim 1, wherein said elongated element is formed with a plurality of effective hinges spaced along its length.
 6. The method of claim 5, wherein said effective hinges are at an oblique angle to a direction of elongation of the elongated element such that said curved configuration of said elongated element exhibits three-dimensional curvature.
 7. The method of claim 6, wherein the curved configuration includes a plurality of non-coplanar loops.
 8. The method of claim 6, wherein the curved configuration includes a conical spiral.
 9. The method of claim 6, wherein the curved configuration includes a helix.
 10. The method of claim 6, wherein the curved configuration includes at least one loop closed on itself so as to generate a region of overlap, and wherein lateral surfaces of said elongated element are formed with complementary interlocking features so as to inhibit lateral displacement of one region of said at least one loop relative to an overlapping portion of said at least one loop.
 11. The method of claim 10, wherein said at least one loop is implemented as a plurality of loops in at least partially overlapping relation.
 12. A method for stabilizing the spinal column of the body of a mammalian subject, the method comprising the steps of (a) providing an elongated element having a plurality of effective hinges, said elongated element being configured such that: (i) said elongated element assumes a substantially straight state for introduction into the body; and (ii) said elongated element is deflected at said effective hinges to assume a curved configuration within the body; (b) introducing the elongated element into the spinal column in the substantially straight state; (c) causing the elongated element to assume the curved configuration within the spinal column, thereby defining an at least partial enclosure; and (d) introducing a quantity of biocompatible structural filler material into the at least partial enclosure so as to stabilize the spinal column.
 13. The method of claim 12, wherein said curved configuration is deployed within a vertebral body such that said curved configuration and said filler material achieve kyphoplasty.
 14. The method of claim 12, wherein said curved configuration is deployed between two vertebral bodies such that said curved configuration and said filler material achieve fusion of the two vertebral bodies.
 15. The method of claim 12, wherein said biocompatible structural filler material comprises at least one material selected from the group of materials consisting of: bone cement; flexible biocompatible fillers; and osteo-inductive materials for promoting bone growth; bone grafts; and bone marrow.
 16. The method of claim 12, wherein said effective hinges are at an oblique angle to a direction of elongation of the elongated element such that said curved configuration of said elongated element exhibits three-dimensional curvature
 17. The method of claim 16, wherein the curved configuration includes a plurality of non-coplanar loops.
 18. The method of claim 16, wherein the curved configuration includes a helix.
 19. The method of claim 16, wherein the curved configuration includes at least one loop closed on itself so as to generate a region of overlap, and wherein lateral surfaces of said elongated element are formed with complementary interlocking features so as to inhibit lateral displacement of one region of said at least one loop relative to an overlapping portion of said at least one loop.
 20. The method of claim 19, wherein said at least one loop is implemented as a plurality of loops in at least partially overlapping relation. 